The invention relates to an apparatus for the treatment of material, especially for the thermal and/or chemical treatment of meal-form raw material.
Such apparatus is used in particular for the calcination of meal-form cement raw material. In that case, the exhaust gas flow of a sintering stage (kiln) and the outgoing air flow of a cooling stage (tertiary air) are used jointly in the fuel-fed ascending pipeline branch of a calcining stage for calcination of the raw meal. In this connection, the gas-solids dispersion in the calcining stage is diverted from the ascending pipeline branch into a descending pipeline branch, and for the purpose of separating the calcined raw meal from the flow of gas is introduced into the lowest cyclone of a cyclone pre-heater.
To achieve the best possible degree of calcination in this calcining stage, efforts are made to carry out optimum intermixing and fluidisation of the gas-raw meal-fuel dispersion in the calcining stage. Intensive mixing and fluidisation of the dispersion can, on the one hand, improve the thorough combustion of the fuel and the NOx reduction of the calcinator exhaust gases (and at the same time reduce the emission of uncombusted constituents), and, on the other hand, increase the degree of calcination through improved heat transfer from the fuel to the material.
Various solutions for fluidisation and mixing of the dispersion in the calcining stage are already known from practice. For example, obstructions were built into the ascending and descending pipeline branch or a fluidisation chamber was provided in the region of the upper change of direction.
EP-B-0 497 937, for example, discloses a calcining stage in which, in the region of its change in flow direction, there is provided a fluidisation chamber, in which at least a fraction of the coarse grain particles are separated from the gas-solids dispersion, which fraction is then re-introduced into a branch of the calcining stage upstream and/or downstream of the fluidisation chamber.
A fluidisation chamber is furthermore known from EP-A-0 526 770. In its upper region, it has an opening for tangential entry of the gas-solid dispersion, and at its underside a central opening for discharge of the fluidised gas-solids dispersion. In this instance it is possible to divert part of the solids in the region of the fluidisation chamber and to re-circulate it again into the ascending pipeline branch.
Further, DE-A-37 35 825 discloses an apparatus for calcining powder-form material, in which a fluidisation head is provided in the deflection region of an ascending or descending pipeline branch.
A double change in direction is also known from practice, in which the ascending pipeline branch discharges from above via a 180xc2x0 elbow into a separator funnel. From this funnel, the dispersion is guided upwards via a second 180xc2x0 elbow, which merges into the descending pipeline branch. A part of the relatively coarse solids particles is separated out downwards in the funnel and re-circulated to the ascending pipeline branch. This double change in direction does produce a very good degree of mixing, but also causes a relatively great pressure loss.
Finally, DE-A-27 51 876 discloses a calcining stage illustrated very diagrammatically in an apparently angular arrangement of piping. More specific structural details of the diversion zone cannot be derived from this schematic illustration, however.
The invention is therefore based on the problem of optimising an apparatus of the kind mentioned in the introduction in respect of the degree of mixing and pressure loss. That problem is solved in accordance with claim 1 in that the diversion zone is formed by a diversion chamber that has a first section that is widened with respect to the cross-section of the ascending pipeline branch and is bounded upwardly by a deflecting wall oriented substantially transversely to the direction of flow of the material entering the diversion chamber via the ascending pipeline branch, adjoining which first section is at least one second section that runs obliquely downwards and tapers conically to the cross-section of the descending pipeline branch.
In accordance with claim 2, the problem is solved in that the diversion zone is formed by a diversion chamber that has a first section widening conically with respect to the ascending pipeline branch and a second section that is bounded by a deflecting wall oriented substantially transversely to the direction of flow of the material entering the diversion chamber via the ascending pipeline branch, wherein the descending pipeline branch projecting in the manner of an immersion pipe into the diversion chamber is lead obliquely downwards out of the diversion chamber.